Oracle studied how to retrim to add more load to the back of the wing. “The boat had lee helm,” Speer said. “You know that kills upwind speed. It was clear that we needed to retrim, so we raked the wing aft—and no, that didn’t work. It turned out that when we powered-off the upper elements—when we added twist aloft—the center of effort shifted down and forward. There was no relief in that. So instead we opened the slot. That gave us less lift on the main element and more lift on the flap [which funnels air aft]. Over the course of the regatta we increased the traveler load by 50 percent. That eliminated lee helm, helped the boat point, and simply made us faster upwind.

The essence of a feedback control system is the system works on the difference between what you want and what actually exists. This difference in control engineering parlance is called the error signal. It can be anything, as long as there is this difference operation is going on. The difference can be electrical, as when an electronic sensor provides a measurement and the subtraction is done in the control computer. But you can also set it up so the difference is done mechanically. This is what OTUSA did.

Modern sports, at the highest level, have become extraordinarily sophisticated, and with that sophistication comes extraordinary complexity.